Inbred corn line PHN18

ABSTRACT

According to the invention, there is provided an inbred corn line, designated PHN18. This invention thus relates to the plants and seeds of inbred corn line PHN18 and to methods for producing a corn plant produced by crossing the inbred line PHN18 with itself or with another corn plant. This invention further relates to hybrid corn seeds and plants produced by crossing the inbred line PHN18 with another corn line or plant.

FIELD OF THE INVENTION

This invention is in the field of corn breeding, specifically relating to an inbred corn line designated PHN18.

BACKGROUND OF THE INVENTION

The goal of plant breeding is to combine in a single variety or hybrid various desirable traits. For field crops, these traits may include resistance to diseases and insects, tolerance to heat and drought, reducing the time to crop maturity, greater yield, and better agronomic quality. With mechanical harvesting of many crops, uniformity of plant characteristics such as germination and stand establishment, growth rate, maturity, and plant and fruit height, is important.

Field crops are bred through techniques that take advantage of the plant's method of pollination. A plant is self-pollinated if pollen from one flower is transferred to the same or another flower of the same plant. A plant is cross-pollinated if the pollen comes from a flower on a different plant.

Plants that have been self-pollinated and selected for type for many generations become homozygous at almost all gene loci and produce a uniform population of true breeding progeny. A cross between two homozygous lines produces a uniform population of hybrid plants that may be heterozygous for many gene loci. A cross of two plants each heterozygous at a number of gene loci will produce a population of hybrid plants that differ genetically and will not be uniform.

Corn plants (Zea mays L.) can be bred by both self-pollination and cross-pollination techniques. Corn has separate male and female flowers on the same plant, located on the tassel and the ear, respectively. Natural pollination occurs in corn when wind blows pollen from the tassels to the silks that protrude from the tops of the incipient ears.

The development of corn hybrids requires the development of homozygous inbred lines, the crossing of these lines, and the evaluation of the crosses. Pedigree breeding and recurrent selection breeding methods are used to develop inbred lines from breeding populations. Breeding programs combine the genetic backgrounds from two or more inbred lines or various other broad-based sources into breeding pools from which new inbred lines are developed by selfing and selection of desired phenotypes. The new inbreds are crossed with other inbred lines and the hybrids from these crosses are evaluated to determine which of those have commercial potential.

Pedigree breeding starts with the crossing of two genotypes, each of which may have one or more desirable characteristics that is lacking in the other or which complement the other. If the two original parents do not provide all of the desired characteristics, other sources can be included in the breeding population. In the pedigree method, superior plants are selfed and selected in successive generations. In the succeeding generations the heterozygous condition gives way to homogeneous lines as a result of self-pollination and selection. Typically in the pedigree method of breeding five or more generations of selfing and selection is practiced: F₁ →F₂ ; F₂ →F₃ ; F₃ →F₄ ; F₄ →F₅, etc.

Backcrossing can be used to improve an inbred line. Backcrossing transfers a specific desirable trait from one inbred or source to an inbred that lacks that trait. This can be accomplished for example by first crossing a superior inbred (A) (recurrent parent) to a donor inbred (non-recurrent parent), which carries the appropriate gene(s) for the trait in question. The progeny of this cross is then mated back to the superior recurrent parent (A) followed by selection in the resultant progeny for the desired trait to be transferred from the non-recurrent parent. After five or more backcross generations with selection for the desired trait, the progeny will be heterozygous for loci controlling the characteristic being transferred, but will be like the superior parent for most or almost all other genes. The last backcross generation would be selfed to give pure breeding progeny for the gene(s) being transferred.

A single cross hybrid corn variety is the cross of two inbred lines, each of which has a genotype which complements the genotype of the other. The hybrid progeny of the first generation is designated F₁. In the development of hybrids only the F₁ hybrid plants are sought. Preferred F₁ hybrids are more vigorous than their inbred parents. This hybrid vigor, or heterosis, can be manifested in many polygenic traits, including increased vegetative growth and increased yield.

The development of a hybrid corn variety involves three steps: (1) the selection of plants from various germplasm pools; (2) the selfing of the selected plants for several generations to produce a series of inbred lines, which, although different from each other, breed true and are highly uniform; and (3) crossing the selected inbred lines with unrelated inbred lines to produce the hybrid progeny (F₁). During the inbreeding process in corn, the vigor of the lines decreases. Vigor is restored when two unrelated inbred lines are crossed to produce the hybrid progeny (F₁). An important consequence of the homozygosity and homogeneity of the inbred lines is that the hybrid between any two inbreds will always be the same. Once the inbreds that give a superior hybrid have been identified, the hybrid seed can be reproduced indefinitely as long as the homogeneity of the inbred parents is maintained.

A single cross hybrid is produced when two inbred lines are crossed to produce the F₁ progeny. A double cross hybrid is produced from four inbred lines crossed in pairs (A×B and C×D) and then the two F₁ hybrids are crossed again (A×B)×(C×D). Much of the hybrid vigor exhibited by F₁ hybrids is lost in the next generation (F₂). Consequently, seed from hybrid varieties is not used for planting stock.

Corn is an important and valuable field crop. Thus, a continuing goal of plant breeders is to develop high-yielding corn hybrids that are agronomically sound based on stable inbred lines. The reasons for this goal are obvious: to maximize the amount of grain produced with the inputs used and minimize susceptibility of the crop to environmental stresses. To accomplish this goal, the corn breeder must select and develop superior inbred parental lines for producing hybrids. This requires identification and selection of genetically unique individuals which in a segregating population occur as the result of a combination of crossover events plus the independent assortment of specific combinations of alleles at many gene loci which results in specific genotypes. Based on the number of segregating genes, the frequency of occurrence of an individual with a specific genotype is less than 1 in 10,000. Thus, even if the entire genotype of the parents has been characterized and the desired genotype is known, only a few if any individuals having the desired genotype may be found in a large F₂ or S₀ population. Typically, however, the genotype of neither the parents nor the desired genotype is known in any detail.

At Pioneer Hi-Bred International, a typical corn research station has a staff of four, and 20 acres of breeding nursery. Those researchers plant those 20 acres with 25,000 nursery rows, 15,000 yield test plots in 10-15 yield test sites, and one or two disease-screening nurseries. Employing a temporary crew of 20 to 30 pollinators, the station makes about 65,000 hand pollinations per growing season, and produces from three to ten new inbreds which are proposed for commercial use each year. Over the 32 Pioneer research stations in North America, this amounts to from about 100 to 300 new inbreds proposed each year from over 2,000,000 pollinations. Of those, less than 50 and more commonly less than 30 are actually selected for commercial use.

SUMMARY OF THE INVENTION

According to the invention, there is provided a novel inbred corn line, designated PHN18. This invention thus relates to the seeds of inbred corn line PHN18, to the plants of inbred corn line PHN18, and to methods for producing a corn plant produced by crossing the inbred line PHN18 with itself or another corn line. This invention further relates to hybrid corn seeds and plants produced by crossing the inbred line PHN18 with another corn line.

DEFINITIONS

In the description and examples that follow, a number of terms are used herein. In order to provide a clear and consistent understanding of the specification and claims, including the scope to be given such terms, the following definitions are provided. ABS is in absolute terms and % MN is percent of the mean for the experiments in which the inbred or hybrid was grown.

BAR PLT=BARREN PLANTS. The percent of plants per plot that were not barren (lack ears).

BRT STK=BRITTLE STALKS. This is a measure of the stalk breakage near the time of pollination, and is an indication of whether a hybrid or inbred would snap or break near the time of flowering under severe winds. Data are presented as percentage of plants that did not snap.

BU ACR=YIELD (BUSHELS/ACRE). Actual yield of the grain at harvest in bushels per acre adjusted to 15.5% moisture.

DRP EAR=DROPPED EARS. A measure of the number of dropped ears per plot and represents the percentage of plants that did not drop ears prior to harvest.

EAR HT=EAR HEIGHT. The ear height is a measure from the ground to the highest placed developed ear node attachment and is measured in inches.

EAR SZ=EAR SIZE. A 1 to 9 visual rating of ear size. The higher the rating the larger the ear size.

EST CNT=EARLY STAND COUNT. This is a measure of the stand establishment in the spring and represents the number of plants that emerge on a per plot basis for the inbred or hybrid.

GDU SHD=GDU TO SHED. The number of growing degree units (GDUs) or heat units required for an inbred line or hybrid to have approximately 50 percent of the plants shedding pollen and is measured from the time of planting. Growing degree units are calculated by the Barger Method, where the heat units for a 24-hour period are: ##EQU1##

The highest maximum temperature used is 86° F. and the lowest minimum temperature used is 50° F. For each inbred or hybrid it takes a certain number of GDUs to reach various stages of plant development.

GDU SLK=GDU TO SILK. The number of growing degree units required for an inbred line or hybrid to have approximately 50 percent of the plants with silk emergence from time of planting. Growing degree units are calculated by the Barger Method as given in GDU SHD definition.

GRN APP=GRAIN APPEARANCE. This is a 1 to 9 rating for the general appearance of the shelled grain as it is harvested based on such factors as the color of the harvested grain, any mold on the grain, and any cracked grain. High scores indicate good grain quality.

MST=HARVEST MOISTURE. The moisture is the actual percentage moisture of the grain at harvest.

PLT HT=PLANT HEIGHT. This is a measure of the height of the plant from the ground to the tip of the tassel in inches.

POL SC=POLLEN SCORE. A 1 to 9 visual rating indicating the amount of pollen shed. The higher the score the more pollen shed.

POL WT=POLLEN WEIGHT. This is calculated by dry weight of tassels collected as shedding commences minus dry weight from similar tassels harvested after shedding is complete.

It should be understood that the inbred can, through routine manipulation of cytoplasmic factors, be produced in a cytoplasmic male-sterile form which is otherwise phenotypically identical to the male-fertile form.

PRM=PREDICTED RM. This trait, predicted relative maturity (RM), is based on the harvest moisture of the grain. The relative maturity rating is based on a known set of checks and utilizes standard linear regression analyses and is referred to as the Comparative Relative Maturity Rating System which is similar to the Minnesota Relative Maturity Rating System.

RT LDG=ROOT LODGING. Root lodging is the percentage of plants that do not root lodge; plants that lean from the vertical axis at an approximately 30° angle or greater would be counted as root lodged.

SCT GRN=SCATTER GRAIN. A 1 to 9 visual rating indicating the amount of scatter grain (lack of pollination or kernel abortion) on the ear. The higher the score the less scatter grain.

SDG VGR=SEEDLING VIGOR. This is the visual rating (1 to 9) of the amount of vegetative growth after emergence at the seedling stage (approximately five leaves). A higher score indicates better vigor.

SEL IND=SELECTION INDEX. The selection index gives a single measure of the hybrid's worth based on information for up to five traits. A corn breeder may utilize his or her own set of traits for the selection index. One of the traits that is almost always included is yield. The selection index data presented in the tables represent the mean value averaged across testing stations.

STA GRN=STAY GREEN. Stay green is the measure of plant health near the time of black layer formation (physiological maturity). A high score indicates better late-season plant health.

STK CNT=NUMBER OF PLANTS. This is the final stand or number of plants per plot.

STK LDG=STALK LODGING. This is the percentage of plants that did not stalk lodge (stalk breakage) as measured by either natural lodging or pushing the stalks and determining the percentage of plants that break below the ear.

TAS BLS=TASSEL BLAST. A 1 to 9 visual rating was used to measure the degree of blasting (necrosis due to heat stress) of the tassel at time of flowering. A 1 would indicate a very high level of blasting at time of flowering, while a 9 would have no tassel blasting.

TAS SZ=TASSEL SIZE. A 1 to 9 visual rating was used to indicate the relative size of the tassel. The higher the rating the larger the tassel.

TAS WT=TASSEL WEIGHT. This is the average weight of a tassel (grams) just prior to pollen shed.

TEX EAR=EAR TEXTURE. A 1 to 9 visual rating was used to indicate the relative hardness (smoothness of crown) of mature grain. A 1 would be very soft (extreme dent) while a 9 would be very hard (flinty or very smooth crown).

TILLER=TILLERS. A count of the number of tillers per plot that could possibly shed pollen was taken. Data is given as percentage of tillers: number of tillers per plot divided by number of plants per plot.

TST WT=TEST WEIGHT (UNADJUSTED). The measure of the weight of the grain in pounds for a given volume (bushel).

TST WTA=TEST WEIGHT ADJUSTED. The measure of the weight of the grain in pounds for a given volume (bushel) adjusted for percent moisture.

YLD=YIELD. It is the same as BU ACR ABS.

YLD SC=YIELD SCORE. A 1 to 9 visual rating was used to give a relative rating for yield based on plot ear piles. The higher the rating the greater visual yield appearance.

MDM CPX=Maize Dwarf Mosaic Complex (MDMV=Maize Dwarf Mosaic Virus & MCDV=Maize Chlorotic Dwarf Virus): Visual rating (1-9 score) where a "1" is very susceptible and a "9" is very resistant.

SLF BLT=Southern Leaf Blight (Bipolaris maydis, Helminthosporium maydis): Visual rating (1-9 score) where a "1" is very susceptible and a "9" is very resistant.

NLF BLT=Northern Leaf Blight (Exserohilum turcicum, H. turcicum): Visual rating (1-9 score) where a "1" is very susceptible and a "9" is very resistant.

COM RST=Common Rust (Puccinia sorghi): Visual rating (1-9 score) where a "1" is very susceptible and a "9" is very resistant.

GLF SPT=Gray Leaf Spot (Cercospora zeae-maydis): Visual rating (1-9 score) where a "1" is very susceptible and a "9" is very resistant.

STW WLT=Stewart's Wilt (Erwinia stewartii): Visual rating (1-9 score) where a "1" is very susceptible and a "9" is very resistant.

HD SMT=Head Smut (Sphacelotheca reiliana): Percentage of plants that did not have infection.

EAR MLD=General Ear Mold: Visual rating (1-9 score) where a "1" is very susceptible and a "9" is very resistant. This is based on overall rating for ear mold of mature ears without determining specific mold organism, and may not be predictive for a specific ear mold.

ECB DPE=Dropped ears due to European Corn Borer (Ostrinia nubilalis): Percentage of plants that did not drop ears under second brood corn borer infestation.

ECB 2SC=European Corn Borer Second Brood (Ostrinia nubilalis): Visual rating (1-9 score) of post flowering damage due to infestation by European Corn Borer. A "1" is very susceptible and a "9" is very resistant.

ECB 1LF=European Corn Borer First Brood (Ostrinia nubilalis): Visual rating (1-9 score) of pre-flowering leaf feeding by European Corn Borer. A "1" is very susceptible and a "9" is very resistant.

DETAILED DESCRIPTION OF THE INVENTION

Inbred corn line PHN18 is a white, dent corn inbred that is best suited as a female in crosses for producing first generation F1 corn hybrids. PHN18 is adapted to most areas of the United States. The inbred can be used to produce hybrids from approximately 121-135 relative maturity based on the Minnesota Relative Maturity Rating System for harvest moisture of grain. The inbred has hard textured grain with good stay green and plant health. PHN18 is early flowering with good stalk strength. In hybrid combination, PHN18 has good combining ability.

The inbred has shown uniformity and stability within the limits of environmental influence for all the traits as described in the Variety Description Information (Table 1) that follows. Most of the data in the Variety Description information was collected at Johnston, Iowa. The inbred has been self-pollinated and ear-rowed a sufficient number of generations with careful attention paid to uniformity of plant type to ensure homozygosity and phenotypic stability. The line has been increased both by hand and in isolated fields with continued observation for uniformity. No variant traits have been observed or are expected in PHN18.

Inbred corn line PHN18, being substantially homozygous, can be reproduced by planting seeds of the line, growing the resulting corn plants under self-pollinating or sib-pollinating conditions with adequate isolation, and harvesting the resulting seed, using techniques familiar to the agricultural arts.

                  TABLE 1     ______________________________________     VARIETY DESCRIPTION INFORMATION     INBRED = PHN18     Type: Dent Region Best Adapted: Most Regions     ______________________________________     A.  Maturity: Average across maturity zones. Zone: 0         GDU Shed: 1460         GDU Silk: 1480         No. Reps: 29     B.  Plant Characteristics:         Plant height (to tassel tip): 204 cm         Length of top ear internode: 12 cm         Number of ears per stalk: Single         Ear height (to base of top ear): 72 cm         Number of tillers: None         Cytoplasm type: Normal     C.  Leaf:         Color: Dark Green (B14)         Angle from Stalk: <30 degrees         Marginal Waves: Few (WF9)         Number of Leaves (mature plants): 17         Sheath Pubescence: Medium (WF9)         Longitudinal Creases: Few (OH56A)         Length (Ear node leaf): 73 cm         Width (widest point, ear node leaf): 8 cm     D.  Tassel:         Number lateral branches: 4         Branch Angle from central spike: <30 degrees         Pollen Shed: Light (WF9) based on Pollen Yield Test         (54% of experiment means)         Peduncle Length (top leaf to basal branches): 23 cm         Anther Color: Yellow         Glume Color: Green     E.  Ear (Husked Ear Data Except When Stated Otherwise):         Length: 15 cm         Weight: 114 gm         Mid-point Diameter: 43 mm         Silk Color: Green         Husk Extension (Harvest stage): Medium (barely covering         ear)         Husk Leaf: Long (>15 cm)         Taper of Ear: Slight         Position of Shank (dry husks): Horizontal         Kernel Rows: Straight, Distinct Number = 18         Husk Color (fresh): Light Green         Husk Color (dry): Buff         Shank Length: 11 cm         Shank (No. of internodes): 7     F.  Kernel (Dried):         Size (from ear mid-point)         Length: 10 mm         Width: 7 mm         Thick: 5 mm         Shape Grade (% rounds): 20-40 (38% medium round based         on Parent Test Data)         Pericarp Color: Colorless         Aleurone Color: Homozygous White         Endosperm Color: White         Endosperm Type: Normal Starch         Gm Wt/100 Seeds (unsized): 23 gm     G.  Cob:         Diameter at mid-point: 27 mm         Strength: Strong         Color: White     H.  Diseases:         Corn Lethal Necrosis (MCMV = Maize Chlorotic mottle         Virus and MDMV = Maize Dwarf Mosaic Virus):         Susceptible         Maize Dwarf Mosaic Complex (MDMV & MCDV = Maize         Dwarf Virus): Susceptible         Anthracnose Stalk Rot (C. graminicola): Susceptible         S. Leaf Blight (B. maydis): Susceptible         N. Leaf Blight (E. turcicum): Intermediate         Common Rust (P. sorghi): Resistant         Southern Rust (P. polysora): Susceptible         Gray Leaf spot (C. zeae): Susceptible         Stewart's Wilt (C. stewartii): Intermediate         Goss's Wilt (C. nebraskense): Highly Resistant         Downy mildew (S. sorghi): Highly Resistant         Fusarium Ear Mold (F. moniliforme): Resistant     I.  Insects:         European Corn Borer-1 Leaf Damage (Pre-flowering):         Susceptible         European Corn Borer-2 (Post-flowering): Intermediate         The above descriptions are based on a scale of 1-9, 1 being         highly susceptible, 9 being highly resistant.         S (Susceptible): Would generally represent a score of 1-3.         I (Intermediate): Would generally represent a score of         4-5.         R (Resistant): Would generally represent a score of 6-7.         H (Highly Resistant): Would generally represent a score of         8-9. Highly resistant does not         imply the inbred is immune.     J.  Variety Most Closely Resembling:     Character Inbred     Maturity  PHT60     Usage     PHT60     ______________________________________

In interpreting the foregoing color designations, reference may be had to the Munsell Glossy Book of Color, a standard color reference.

PHT60 (PVP Certificate No. 8800219) is a Pioneer Hi-Bred International, Inc. proprietary inbred.

Data for Items B, C, D, E, F, and G is based primarily on a maximum of four reps from Johnston, Iowa grown in 1990 and 1991, plus description information from the maintaining station.

ELECTROPHORESIS RESULTS Isozyme Genotypes for PHN18

Isozyme data were generated for inbred corn line PHN18 according to the procedures described in Stuber, C. W., Wendel, J. F., Goodman, M. M., and Smith, J. S. C., "Techniques and Scoring Procedures for Starch Gel Electrophoresis of Enzymes from Maize (Zea mays L.)", Technical Bulletin No. 286, North Carolina Agricultural Research Service, North Carolina State University, Raleigh, N.C. (1988). The data in Table 2 compares PHN18 with its parents, PHDK6 and PHNN2.

                  TABLE 2     ______________________________________     ELECTROPHORESIS RESULTS FOR PHN18     AND ITS PARENTS PHDK6 AND PHNN2                     PARENTS     LOCI     PHN18        PHDK6    PHNN2     ______________________________________     ACP1     2            2        2     ADH1     4            4        4     CAT3     N            9        N     DIA1     12           12       8     GOT1     4            4        4     GOT2     4            4        4     GOT3     4            4        4     IDH1     4            4        4     IDH2     6            6        6     MDH1     6            6        6     MDH2     3.5          3.5      3.5     MDH3     16           16       16     MDH4     12           12       12     MDH5     12           12       12     MMM      4            4        4     PGM1     9            9        9     PGM2     4            4        4     PGD1     2            3.8      2     PGD2     5            5        5     PHI1     4            4        4     ______________________________________

INDUSTRIAL APPLICABILITY

This invention also is directed to methods for producing a corn plant by crossing a first parent corn plant with a second parent corn plant wherein the first or second parent corn plant is an inbred corn plant from the line PHN18. Further, both first and second parent corn plants can come from the inbred corn line PHN18. Thus, any such methods using the inbred corn line PHN18 are part of this invention: selfing, backcrosses, hybrid production, crosses to populations, and the like. All plants produced using inbred corn line PHN18 as a parent are within the scope of this invention. Advantageously, the inbred corn line is used in crosses with other, different, corn inbreds to produce first generation (F₁) corn hybrid seeds and plants with superior characteristics.

As used herein, the term plant includes plant cells, plant protoplasts, plant cell tissue cultures from which corn plants can be regenerated, plant calli, plant clumps, and plant cells that are intact in plants or parts of plants, such as embryos, pollen, flowers, kernels, ears, cobs, leaves, husks, stalks, roots, root tips, anthers, silk and the like.

Duncan, Williams, Zehr, and Widholm, Planta, (1985) 165:322-332 reflects that 97% of the plants cultured which produced callus were capable of plant regeneration. Subsequent experiments with both inbreds and hybrids produced 91% regenerable callus which produced plants. In a further study in 1988, Songstad, Duncan & Widholm in Plant Cell Reports (1988), 7:262-265 reports several media additions which enhance regenerability of callus of two inbred lines. Other published reports also indicated that "nontraditional" tissues are capable of producing somatic embryogenesis and plant regeneration. K. P. Rao, et al., Maize Genetics Cooperation Newsletter, 60:64-65 (1986), refers to somatic embryogenesis from glume callus cultures and B. V. Conger, et al., Plant Cell Reports, 6:345-347 (1987) indicates somatic embryogenesis from the tissue cultures of maize leaf segments. Thus, it is clear from the literature that the state of the art is such that these methods of obtaining plants are, and were, "conventional" in the sense that they are routinely used and have a very high rate of success.

Tissue culture of corn is described in European Patent Application, publication 160,390, incorporated herein by reference. Corn tissue culture procedures are also described in Green and Rhodes, "Plant Regeneration in Tissue Culture of Maize," Maize for Biological Research (Plant Molecular Biology Association, Charlottesville, Va. 1982, at 367-372) and in Duncan, et al., "The Production of Callus Capable of Plant Regeneration from Immature Embryos of Numerous Zea Mays Genotypes," 165 Planta 322-332 (1985). Thus, another aspect of this invention is to provide cells which upon growth and differentiation produce corn plants having the physiological and morphological characteristics of the inbred line PHN18.

Corn is used as human food, livestock feed, and as raw material in industry. The food uses of corn, in addition to human consumption of corn kernels, include both products of dry- and wet-milling industries. The principal products of corn dry milling are grits, meal and flour. The corn wet-milling industry can provide corn starch, corn syrups, and dextrose for food use. Corn oil is recovered from corn germ, which is a by-product of both dry- and wet-milling industries.

Corn, including both grain and non-grain portions of the plant, is also used extensively as livestock feed, primarily for beef cattle, dairy cattle, hogs, and poultry.

Industrial uses of corn are mainly from corn starch in the wet-milling industry and corn flour in the dry-milling industry. The industrial applications of corn starch and flour are based on functional properties, such as viscosity, film formation, adhesive properties, and ability to suspend particles. The corn starch and flour have application in the paper and textile industries. Other industrial uses include applications in adhesives, building materials, foundry binders, laundry starches, explosives, oil-well muds, and other mining applications.

Plant parts other than the grain of corn are also used in industry. Stalks and husks are made into paper and wallboard and cobs are used for fuel and to make charcoal.

The seed of inbred corn line PHN18, the plant produced from the inbred seed, the hybrid corn plant produced from the crossing of the inbred, hybrid seed, and various parts of the hybrid corn plant can be utilized for human food, livestock feed, and as a raw material in industry.

EXAMPLE 3 Inbred and Hybrid Performance of PHN18

In the examples that follow, the traits and characteristics of inbred corn line PHN18 are given as a line and in hybrid combination. The data collected on inbred corn line PHN18 is presented for the key characteristics and traits.

The parents of PHN18 are no longer used in Pioneer's Breeding Program, therefore, no data is available comparing the parents to PHN18.

Table 3A compares PHN18 to PHW17. PHW17 is a Pioneer Proprietary Inbred with a similar genetic background, similar usage and performance in the area where PHN18 is adapted. The results show PHN18 is lower yielding than PHW17. PHN18 sheds (GDU Shed) later, but silks (GDU Silk) earlier than PHW17. PHN18 has a smaller tassel and lower scattergrain score than PHW17. First brood European corn borer resistance is better for PHN18 compared to PHW17.

The results in Table 4A compare PHN18 to PHW20 crossed to the same inbred testers. The results show the PHN18 hybrids have higher yield, grain harvest moisture, and test weight than the PHW20 hybrids. The PHN18 hybrids shed (GDU Shed) later than the PHW20 hybrids. The PHN18 hybrids are more susceptible to stalk and root lodging than the PHW20 hybrids. The PHN18 hybrids have better stay green, grain appearance, and seedling vigor than the PHW20 hybrids.

Table 4B compares PHN18 to PHN34 crossed to the same inbred testers. The PHN18 hybrids have higher yield and grain harvest moisture compared to the PHN34 hybrids. The PHN18 hybrids are more susceptible to root and stalk lodging than the PHN34 hybrids. The PHN18 hybrids have better grain appearance and seedling vigor and slightly higher early stand count than the PHN34 hybrids. The PHN18 hybrids are slightly shorter with lower ear placement than the PHN34 hybrids.

Tables 5 through 7 compare PHN18 hybrids to Pioneer Brand Hybrids 3283W, 3372W, and 3463W, respectively. Each hybrid has a parent in common with the PHN18 hybrid other than PHN18. The hybrids are adapted to much of the same area as the PHN18 hybrids. Table 5 compares a PHN18 hybrid to 3283W. The PHN18 hybrid is lower yielding, but has higher grain harvest moisture and test weight compared to 3283W. The PHN18 hybrid is taller with higher ear placement and flowers (GDU Shed and GDU Silk) earlier than 3283W. The PHN18 hybrid has better grain appearance and stay green than 3283W. The PHN18 hybrid has similar stalk lodging, but is more susceptible to root lodging and brittle stalks compared to 3283W.

Table 6 compares a PHN18 hybrid to Pioneer Brand Hybrid 3372W. The results show the PHN18 hybrid has higher yield and grain harvest moisture compared to 3372W. The PHN18 hybrid has fewer barren plants than 3372W. The PHN18 hybrid is shorter with lower ear placement and flowers (GDU Shed and GDU Silk) earlier than 3372W. The PHN18 hybrid and 3372W have similar grain appearance, but the PHN18 hybrid has better stay green. The PHN18 hybrid and 3372W have similar stalk lodging resistance, but the PHN18 hybrid is more susceptible to root lodging and has more brittle stalks compared to 3372W.

The results in Table 7, comparing a PHN18 hybrid to Pioneer Brand Hybrid 3463W, show the PHN18 hybrid has higher yield, grain harvest moisture, and test weight than 3463W. The PHN18 hybrid is slightly taller, but has lower ear placement than 3463W. The PHN18 hybrid has better seedling vigor and a higher early stand count compared to 3463W. The PHN18 hybrid flowers (GDU Shed and GDU Silk) later than 3463W. Grain appearance and stay green is significantly better for the PHN18 hybrid compared to 3463W. The PHN18 hybrid has better stalk lodging resistance, but is more susceptible to root lodging and has more brittle stalks than 3463W.

                  TABLE 3A     ______________________________________     PAIRED INBRED COMPARISON DATA     VARIETY #1 = PHN18     VARIETY #2 = PHW17     * = 10% SIG + = 5% SIG # = 1% SIG     ______________________________________                       YLD    EAR   GDU   GDU   TAS               VAR     SC     SZ    SHD   SLK   SZ     DEPT      #       ABS    ABS   ABS   ABS   ABS     ______________________________________     TOTAL SUM 1       6.0    6.0   1460  1460  5.0               2       7.0    6.0   1430  1490  7.0               LOCS    1      1       1     1   1               REPS    1      1       1     1   1               DIFF    1.0    0.0    30    30   2.0               PROB     ______________________________________                       SCT               VAR     GRN     DEPT      #       ABS     ______________________________________     TOTAL SUM 1       6.0               2       8.0               LOCS    1               REPS    1               DIFF    2.0               PROB     ______________________________________               ECB               VAR     1LF     DEPT      #       ABS     ______________________________________     TOTAL SUM 1       6.0               2       4.0               LOCS    1               REPS    1               DIFF    2.0               PROB     ______________________________________

                                      TABLE 4A     __________________________________________________________________________     AVERAGE INBRED BY TESTER PERFORMANCE COMPARING PHN18 TO PHW20     CROSSED TO THE SAME INBRED TESTERS AND GROWN IN THE SAME     EXPERIMENTS. ALL VALUES ARE EXPRESSED AS PERCENT OF THE     EXPERIMENT MEAN EXCEPT PREDICTED RM, SELECTION INDEX,     AND YIELD (BU/ACR).     __________________________________________________________________________                      SEL                         BU       GDU PRM STK RT            INBRED                  PRM IND                         ACR                            YLD                               MST                                  SHD SHD LDG LDG     __________________________________________________________________________     TOTAL  REPLIC.                  40  40 40 40 40 12  4   24  4     MEAN WTS            PHN18 121 109                         140                            112                               116                                  100 111 98  90     MEAN WTS            PHW20 112 98 121                            97 96 95  108 103 105            DIFF. 9   11 18 15 21 4   3   5   15     __________________________________________________________________________                  STA TST GRN SDG EST                                     STK                                        PLT                                           EAR                                              DRP            INBRED                  GRN WTA APP VGR CNT                                     CNT                                        HT HT EAR     __________________________________________________________________________     TOTAL  REPLIC.                  32  40  40  12  24 40 24 24 24     MEAN WTS            PHN18 120 101 110 122 100                                     101                                        101                                           98 100     MEAN WTS            PHW20 62  99  94  74  99 100                                        100                                           99 99            DIFF. 57  2   16  48  1  1  1  2  1     __________________________________________________________________________

                                      TABLE 4B     __________________________________________________________________________     AVERAGE INBRED BY TESTER PERFORMANCE COMPARING PHN18 TO PHN34     CROSSED TO THE SAME INBRED TESTERS AND GROWN IN THE SAME     EXPERIMENTS. ALL VALUES ARE EXPRESSED AS PERCENT OF THE     EXPERIMENT MEAN EXCEPT PREDICTED RM, SELECTION INDEX,     AND YIELD (BU/ACR).     __________________________________________________________________________                      SEL                         BU       GDU PRM STK RT            INBRED                  PRM IND                         ACR                            YLD                               MST                                  SHD SHD LDG LDG     __________________________________________________________________________     TOTAL  REPLIC.                  80  80 80 80 80 21  5   48  5     MEAN WTS            PHN18 116 108                         137                            110                               108                                  100 112 97  84     MEAN WTS            PHN34 110 95 115                            92 93 102 112 100 102            DIFF. 6   13 22 18 14 2   1   3   18     __________________________________________________________________________                  STA TST GRN SDG EST                                     STK                                        PLT                                           EAR                                              DRP            INBRED                  GRN WTA APP VGR CNT                                     CNT                                        HT HT EAR     __________________________________________________________________________     TOTAL  REPLIC.                  52  80  80  15  48 80 42 42 42     MEAN WTS            PHN18 98  100 108 115 101                                     101                                        100                                           98 100     MEAN WTS            PHN34 69  101 111 88  98 99 102                                           105                                              100            DIFF. 29  1   3   26  3  2  2  7  0     __________________________________________________________________________

                                      TABLE 5     __________________________________________________________________________     PHN18 HYBRID COMPARED TO PIONEER HYBRID 3283W     VARIETY #1 = PHN18 HYBRID     VARIETY #2 = 3283W     __________________________________________________________________________                BU  BU      PLT EAR SDG EST DRP            VAR ACR ACR MST HT  HT  VGR CNT EAR     DEPT   #   ABS % MN                        ABS ABS ABS ABS ABS ABS     __________________________________________________________________________     TOTAL  1   148.5                    100 20.1                            102.8                                44.4                                    7.0 60.7                                            99.7     SUM    2   152.0                    102 18.7                            99.3                                42.1                                    6.3 59.9                                            99.6            LOCS                105 105 106 50  50  47  66  27            REPS                200 200 201 99  99  90  129 48            DIFF                3.52                    1.4 3.6 2.3 0.7 0.8 0.1            PROB                .047+                    .096*                        .000                            .000#                                .000#                                    .000#                                        .128                                            .489     __________________________________________________________________________                 GDU GDU TST GRN STA STK RT  BRT             VAR SHD SLK WTA APP GRN LDG LDG STK     DEPT    ABS ABS ABS ABS ABS ABS ABS ABS ABS     __________________________________________________________________________     TOTAL SUM             1   1376                     1378                         60.2                             7.8 6.8 96.7                                         84.9                                             94.1             2   1390                     1407                         58.0                             6.9 5.3 96.6                                         92.5                                             99.0             LOCS                 32  8   104 49  62  89  26  5             REPS                 61  20  197 97  120 166 51  10             DIFF                 14  29  2.1 0.8 1.5 0.1 3.6 4.9             PROB                 .007#                     .021+                         .000#                             .000#                                 .000#                                     .908                                         .036+                                             .271     __________________________________________________________________________

                                      TABLE 6     __________________________________________________________________________     PHN18 HYBRID COMPARED TO PIONEER HYBRID 3372W     VARIETY #1 = PHN18 HYBRID     VARIETY #2 = 3372W     __________________________________________________________________________                 BU  BU      BAR PLT EAR SDG EST DRP             VAR ACR ACR MST PLT HT  HT  VGR CNT EAR     DEPT    #   ABS % MN                         ABS ABS ABS ABS ABS ABS ABS     __________________________________________________________________________     TOTAL   1   145.9                     100 20.1                             85.1                                 103.1                                     44.5                                         6.9 60.7                                                 99.7     SUM     2   133.9                     91  18.3                             68.6                                 106.9                                     47.2                                         5.3 59.3                                                 99.8             LOCS                 135 135 137 2   65  65  68  85  47             REPS                 241 241 244 4   120 120 121 155 78             DIFF                 12.1                     9   1.8 16.6                                 3.7 2.7 1.6 1.4 0.1             PROB                 .000#                     .000#                         .000#                             .121                                 .000#                                     .000#                                         .000#                                             .005#                                                 .541     __________________________________________________________________________                      GDU GDU TST GRN STA STK RT  BRT                  VAR SHD SLK WTA APP GRN LDG LDG STK     DEPT         ABS ABS ABS ABS ABS ABS ABS ABS ABS     __________________________________________________________________________     TOTAL SUM    1   1382                          1385                              60.2                                  7.6 7.0 96.8                                              86.2                                                  94.7                  2   1413                          1456                              60.0                                  7.5 5.7 97.2                                              95.2                                                  99.0                  LOCS                      44  12  134 74  84  115 40  6                  REPS                      78  24  238 131 150 204 73  11                  DIFF                      31  71  0.2 0.1 1.3 0.4 8.9 4.3                  PROB                      .000#                          .000#                              .134                                  .558                                      .000#                                          .327                                              .000#                                                  .219     __________________________________________________________________________

                                      TABLE 7     __________________________________________________________________________     PHN18 HYBRID COMPARED TO PIONEER HYBRID 3463W     VARIETY #1 = PHN18 HYBRID     VARIETY #2 = 3463W     __________________________________________________________________________                 BU  BU      BAR PLT EAR SDG EST DRP             VAR ACR ACR MST PLT HT  HT  VGR CNT EAR     DEPT    #   ABS % MN                         ABS ABS ABS ABS ABS ABS ABS     __________________________________________________________________________     TOTAL   1   147.1                     103 20.4                             85.1                                 101.2                                     44.7                                         6.7 61.0                                                 99.8     SUM     2   133.9                     93  17.5                             86.4                                 100.9                                     45.3                                         4.6 56.7                                                 99.3             LOCS                 104 104 105 2   52  52  47  65  53             REPS                 169 169 170 4   85  85  78  107 81             DIFF                 10  3.0 1.3 0.3 0.6 2.1 4.3 0.4             PROB                 .000#                     .000#                         .000#                             .685                                 .595                                     .487                                         .000#                                             .000#                                                 .027+     __________________________________________________________________________                      GDU GDU TST GRN STA STK RT  BRT                  VAR SHD SLK WTA APP GRN LDG LDG STK     DEPT         ABS ABS ABS ABS ABS ABS ABS ABS ABS     __________________________________________________________________________     TOTAL SUM    1   1368                          1376                              60.3                                  7.5 7.3 96.5                                              84.3                                                  93.9                  2   1324                          1351                              58.6                                  7.0 4.3 95.3                                              94.2                                                  98.3                  LOCS                      36  8   103 69  60  89  35  5                  REPS                      57  13  166 110 98  143 62  9                  DIFF                      46  25  1.7 0.5 3.0 1.2 10.0                                                  4.5                  PROB                      .000#                          .040+                              .000#                                  .006#                                      .000#                                          .064*                                              .001#                                                  .219     __________________________________________________________________________

Applicants have made available to the public without restriction a deposit of at least 2500 seeds of Inbred Corn Line PHN18 with the American Type Culture Collection (ATCC), Rockville, Md. 20852 USA, ATCC Deposit No. 97517. The seeds deposited with the ATCC are taken from the same deposit maintained by Pioneer Hi-Bred International, Inc., 700 Capital Square, 400 Locust Street, Des Moines, Iowa 50309 since prior to the filing date of this application. This deposit of the Inbred Corn Line PHN18 will be maintained without restriction in the ATCC depository, which is a public depository, for a period of 30 years, or 5 years after the most recent request, or for the enforceable life of the patent, whichever is longer, and will be replaced if it becomes nonviable during that period. 

What is claimed is:
 1. Inbred corn seed designated PHN18 and having ATCC Accession No.
 97517. 2. A corn plant, and its parts, produced by the seed of claim
 1. 3. A corn plant having all the physiological and morphological characteristics of PHN18, seed of which having been deposited under ATCC Accession No
 97517. 4. A male sterile corn plant, and parts thereof, otherwise having all the physiological and morphological characteristics of the plant of claim
 2. 5. A tissue culture of regenerable cells of inbred corn plant PHN18, seed of which having been deposited under ATCC Accession No 97517, wherein the tissue regenerates plants having all morphological and physiological characteristics of PHN18.
 6. A tissue culture of a plant according to claim 5, the tissue culture selected from the group consisting of leaves, pollen, embryos, roots, root tips, anthers, silk, flowers, kernels, ears, cobs, husks, and stalks, and cells and protoplasts thereof.
 7. A corn plant capable of expressing all the physiological and morphological characteristics of PHN18 regenerated from a tissue culture of PHN18, seed of which having been deposited under ATCC Accession No
 97517. 8. A method of producing a hybrid corn seed comprising the steps of:(a) planting, in pollinating proximity, seed of corn inbred line PHN18, seed of which having been deposited under ATCC Accession No 97517 , and another inbred line; (b) cultivating corn plants resulting from said planting until the time the plants bear flowers; (c) emasculating the flowers of the plants of either inbred line; (d) allowing natural cross pollinating to occurr between said inbred liens; and (e) harvesting seed produced on said emasculated plants of the inbred line.
 9. An F₁ hybrid seed and plant grown thereof, and its parts, produced by crossing inbred corn plant PHN18, seed of which having been deposited under ATCC Accession No 97517, with another, different corn plant.
 10. A tissue culture of tile regenerable cells of the corn plant produced by crossing inbred corn plant PHN18, seed of which having been deposited under ATCC Accession No 97517, with another different corn plant. 